1. Field of the Invention
The present invention relates to a mobile terminal having a function of performing data communication by a plurality of communication systems, such as a mobile terminal which appropriately switches the communication systems.
2. Description of Related Art
At present, a mobile terminal such as a cellular phone has data communication functions such as mail transmission/reception functions or web page access functions in addition to voice communication functions as its basic function.
When data communication is performed by a mobile terminal, the data communication performed via a mobile communication system using a public line network (for example, Code Division Multiple Access (CDMA) or Global System for Mobile Communications (GSM)). On the other hand, there are mobile terminals to which a communication function using a wireless Local Area Network (LAN) is further added.
In a mobile terminal capable of employing a plurality of communication systems such as mobile communication and wireless LAN communication, how to select the communication system using data communication is important. For example, JP-A-2007-181178 discloses a mobile communication terminal having a wireless LAN connection function which reduces power consumption by appropriately selecting the communication system.
When a plurality of available communication systems (within a communication range) exists for a mobile terminal, the communication system to be preferentially used among the plurality of available communication systems may be preset. For example, switching to another communication system is performed to continue data communication when communication has been generated out of range during the data communication with the preferentially used communication system or is performed for data communication when new data communication has been generated.
Billing systems may differ between different communication systems installed to a mobile terminal. For example, a communication system using mobile communication is generally expensive between a communication system using mobile communication and a communication system using a wireless LAN.
When communication is temporarily generated out of range, as described above, the mobile terminal may be automatically switched from a preferentially used communication system (for example, a low-cost wireless LAN) to another communication system (for example, high-cost mobile communication). As a result, when data communication is continued in a state in which a user does not recognize the switching of the communication system, an unintended data communication cost may be added.